The field of the invention is closure caps for containers and more particularly is the provision of a novel closure cap which is formed of thin sheet metal and is adapted to be installed onto the top of a beverage bottle of glass or plastic.
Although not limited thereto, the closure cap of the invention is especially intended for use with glass bottles that are used world wide for containing soft drinks and brewed beverages such as beer and ale. The design and dimensions of the open end of such bottle has been fairly standardized and is designated by the standard DIN6094 in foreign countries, such open end or so-called mouthpiece having a beaded outer rim with an exterior diameter of 26.5 mm.
So far as known there is no commercially available closure cap which is reliably capable of relieving the pressure within a beverage container without blowing off the closure cap. Bottled beverages consist generally of two types, those which are gaseous and those which are still. Both types may be required to pass through autoclaves for pasteurization purposes and thereby are subjected to high pressures produced by the elevated temperatures that are involved. Pasteurization of beer, for example, is effected at a temperature of about 72.degree. C. in which the internal pressure of a container will rise to well over 10 bars (one bar equals 1 megadyne per square centimeter) for a beverage that has about 4 or more grams of carbon dioxide per liter dissolved in the liquid.
In the case of sterilizing liquids which are not gaseous, the autoclave temperatures are from about 123.degree. C. to 133.degree. C. and are maintained at this temperature for up to 40 minutes. Thus, the pressures can and usually do rise to values which can burst containers. This is especially true in the case of glass bottles which are of the refillable type. Fatigue and weaknesses in used bottles are difficult to detect and the result of breakage is loss of the contents in addition to the inconvenience of removing the broken materials from the machinery.
Gaseous beverages such as soft drinks and beer frequently are also subjected to high pressures during storage and transportation and even while in the possession of the user. Heat and agitation of the container will increase the internal pressure and can result in explosions of the containers. There are losses of containers and contents in transportation, storage and even in sales outlets where ambient conditions result in high temperatures. As for the explosion of containers in the possession of users, this is most common with used containers but occurs with new containers as well. There is always a danger to the user of carbonated beverages and, as a consequence, a constant source of expense for bottlers who are required to provide insurance and defend against lawsuits for injuries.
Another problem with prior closure caps has been the crazing and chipping caused by the application of the closure cap to the container and such damage caused by the user when opening the same. This is especially true with the so-called crown caps that are crimped in place with multiple dimples or crimps and which require a bottle opener to remove the same.
There is another disadvantage of prior closure caps of all kinds which is encountered during the opening of the container to gain access to the contents. The counters are under pressure and the degree of pressure is dependent upon the temperature and the amount of agitation to which the container has been subjected the act of opening the container is accepted as adventuresome by users because there is no way of controlling the release of pressure. It can be gradual or explosive, the latter being the most commonly encountered type of relief. The contents of the container may be expelled during the opening to varying degrees causing inconvenience and annoyance also, and the closure cap may fly up dangerously.
It has been difficult if not totally impractical to apply closure caps of a type which are applied by axial engagement to plastic bottles because of the danger of crushing the bottle or collapsing its neck. Therefore, plastic bottles designed to contain beverages generally are provided with screw type upper ends which require expensive screwcap types of closures and special machinery for installation. The cost of the bottles as well as the cost of the closure caps in increased.
There are several types of closure caps besides the crown cork crimped or the crown cork twist-off types which are used on bottles and each has its disadvantages. These are variously known as "Alka", "Rip Cap" and "Maxicap". The latter two have parallel rip lines which pass over the top or crown of the closure so that the user must either pull the tab all the way to divide the closure into three pieces or he must manipulate the cap parts to separate them for removal from the bottle in order to gain access to the contents. There is no need to describe the inconvenience and difficulties with such closure caps. Manipulation of the cut-open parts can result in finger injuries.
The type of closure cap which has been referred to as "Alka" is characterized by a pull tab and a weakened rip line that tears away a portion of the wall of the cap requiring the user to manipulate the remainder of the cap from the bottle.
In the crown cork type of closure cap the sides of the closure cap are ribbed or crimped making it difficult to carry graphic material legibly thereon.